Social anxiety disorder (SAD) runs in families. Parents with SAD may contribute to SAD development in their children in two ways: First, temperamental dispositions for anxiety can be inherited from SAD parents. Second, parents can transmit anxiety environmentally, by (non-verbally) modelling anxious behaviour, or by (verbally) communicating threat/anxiety in social situations. Not all children, however, are equally sensitive to this environmental transmission. Child temperamental dispositions not only increase the risk for SAD, but also enhance sensitivity to environmental transmission. Theoretical accounts highlight the joint influence of parents’ anxious behaviour and child temperamental dispositions on the emergence of SAD. However, the effect of verbal anxiety expressions by SAD parents, and the moderating role of child temperament in the acquisition of social anxiety is currently unknown. This 12-month project, for the first time, examines the causal effects of parents’ verbal anxiety expressions, and its interplay with child temperament on the acquisition of social anxiety. The project is the first one to incorporate child physiology, cognition and behavior to investigate child reactions to strangers in a single multi-method experimental design, in the period preceding the onset of SAD in children (5-6 years). The project has direct implications for prevention of intergenerational SAD transmission.